1. Field of the Invention
This invention relates to a radiation image recording and read-out apparatus for recording a radiation image on a stimulable phosphor, exposing the stimulable phosphor to stimulating rays which cause the stimulable phosphor to emit light in proportion to the stored radiation energy, detecting the emitted light to read out the radiation image, and converting the emitted light into electric signals. This invention particularly relates to a radiation image recording and read-out apparatus which efficiently carries out image recording, image read-out and other processing.
2. Description of the Prior Art
When certain kinds of phosphors are exposed to a radiation such as X-rays, .alpha.-rays .beta.-rays, .gamma.-rays, cathode rays or ultraviolet rays, they store a part of the energy of the radiation. Then, when the phosphor which has been exposed to the radiation is exposed to stimulating rays such as visible light, light is emitted by the phosphor in proportion to the stored energy of the radiation. A phosphor exhibiting such properties is referred to as a stimulable phosphor.
As disclosed in U.S. Pat. No. 4,258,264 and Japanese Unexamined Patent Publication No. 56(1981)-11395, it has been proposed to use a stimulable phosphor in a radiation image recording and reproducing system. Specifically, a recording material provided with a layer of the stimulable phosphor is first exposed to a radiation passing through an object such as the human body to have a radiation image of the object stored thereon, and is then two-dimensionally scanned by stimulating rays such as a laser beam which cause the recording material to emit light in proportion to the stored radiation energy. The light emitted by the recording material upon stimulation thereof is photoelectrically detected and converted to electric image signals by a photodetector, and the radiation image of the object is reproduced as a visible image by use of the image signals on a recording medium such as a photographic film, a display device such as a cathode ray tube (CRT), or the like.
The radiation image recording and reproducing system using a recording material provided with a stimulable phosphor is advantageous over conventional radiography using a silver halide photographic material in that the image can be recorded over a very wide range (latitude) of radiation exposure. More specifically, since the amount of light emitted upon stimulation after the radiation energy is stored on the stimulable phosphor varies over a wide range is proportion to the amount of said stored energy, it is possible to obtain an image having desirable density regardless of the amount of exposure of the recording material provided with the stimulable phosphor to the radiation, by reading out the emitted light with an appropriate read-out gain and converting it into electric signals to reproduce a visible image on a recording medium or a display device.
In the aforesaid radiation image recording and reproducing system, the recording material provided with the stimulable phosphor is used to temporarily store the radiation image in order to reproduce the final visible image therefrom on a final recording medium. For economical reasons, therefore, it is desirable that the recording material provided with the stimulable phosphor be used repeatedly.
Accordingly, the applicant proposed in, for example, Japanese Unexamined Patent Publication No. 58(1983)-200269, a radiation image recording and read-out apparatus which enables efficient circulation and reuse of the stimulable phosphor.
The proposed radiation image recording and read-out apparatus comprises, built in a single apparatus:
(a) a supporting material, PA1 (b) at least one recording material fixed on said supporting material and comprised of a stimulable phosphor layer capable of storing a radiation image, PA1 (c) an image recording section for exposing said recording material to a radiation passing through an object to have a radiation image of the object stored on said recording material, PA1 (d) an image read-out section provided with a stimulating ray irradiation means for irradiating stimulating rays to said recording material carrying said radiation image stored thereon, and a photoelectric read-out means for obtaining electric image signals by reading out light emitted by said recording material in proportion to the stored radiation energy when said recording material is exposed to the stimulating rays, PA1 (f) an erasing section for eliminating the radiation energy remaining on said recording material prior to image recording on said recording material after the radiation image is read out therefrom at said image read-out section, PA1 (i) an endless belt provided with a stimulable phosphor layer, PA1 (ii) a conveyance means for conveying and circulating said endless belt applied around said conveyance means, PA1 (iii) an image recording section provided to face said endless belt for exposing said stimulable phosphor layer to a radiation carrying an image to have the radiation image stored on said stimulable phosphor layer, PA1 (iv) an image read-out section facing said endless belt and provided with a stimulating ray irradiation means for irradiating stimulating rays to said stimulable phosphor layer carrying said radiation image stored thereon, and a photoelectric read-out means for obtaining electric image signals by reading out light emitted by said stimulable phosphor layer in proportion to the stored radiation energy when said stimulable phosphor layer is exposed to the stimulating rays, and PA1 (v) an erasing section provided to face said endless belt for eliminating the radiation energy remaining on said stimulable phosphor layer prior to image recording on said stimulable phosphor layer after the radiation image is read out therefrom at said image read-out section,
(e) a means for circulating said recording material on said supporting material with respect to said image read-out section for enabling reuse of said recording material by repeatedly moving said supporting material and said image read-out section with respect to each other, and
whereby the recording material is efficiently circulated and reused.
In the proposed radiation image recording and read-out apparatus, it is very advantageous that a material comprising an endless supporting belt and a plurality of stimulable phosphor layers overlaid on the endless supporting belt be used as the recording material. In this case, the recording material can be applied around rollers or the like and conveyed and circulated sequentially through the image recording section, the image read-out section and the erasing section. An example of such a configuration is shown in FIG. 5.
With reference to FIG. 5, three stimulable phosphor sheets 102, 102, 102 are fixed on an endless conveyor 101. The conveyor 101 is provided around rollers 103 and 104, and moved in the direction as indicated by the arrow by rotations of the rollers 103 and 104. Around the conveyor 101, an image recording section 110, an image read-out section 120 and an erasing section 130 are disposed sequentially in the direction of conveyance by the conveyor 101.
The image recording section 110 is provided with a radiation source 111 which may be an X-ray source or the like, and stores a radiation image of an object 112 on the stimulable phosphor sheet 102 facing the radiation source 111 via the object 112. The stimulable phosphor sheet 102 carrying the radiation image thus stored thereon is then sent to the image read-out section 120. The image read-out section 120 is provided with a stimulating ray source 121 for emitting stimulating rays 121A such as a laser beam, a light deflector 122 constituted by a galvanometer mirror or the like for deflecting the stimulating rays 121A emitted by the stimulating ray source 121 in the width direction of the conveyor 101, and a photodetector 123 for reading out the light 125 emitted by the stimulable phosphor sheet 102 upon stimulation thereof by the stimulating rays 121A. The photodetector 123 may be constituted by a head-on type photomultiplier, a photoelectric amplification channel plate or the like. The photodetector 123 photoelectrically detects the light 125 emitted by the stimulable phosphor sheet 102 upon stimulation thereof and guided by a light guide member 124. When the image-recorded stimulable phosphor sheet 102 has been sent to the image read-out section 120, the stimulable phosphor sheet 102 is moved normal to the direction of scanning of the stimulating rays 121A, so that the overall surface of the stimulable phosphor sheet 102 is exposed to the stimulating rays 121A and the image read-out is carried out over the overall surface of the stimulable phosphor sheet 102. After the image read-out from the stimulable phosphor sheet 102 is finished, the stimulable phosphor sheet 102 is sent to the erasing section 130 provided with an erasing light source 131. The erasing light source 131 irradiates light having a wavelength within the stimulation wavelength range of the stimulable phosphor sheet 102 onto the stimulable phosphor sheet 102 to cause it to release the radiation energy remaining thereon. The erasing light source 131 may be constituted by, e.g., a tungsten-filament lamp, a halogen lamp, an infrared lamp, or a laser source as disclosed in U.S. Pat. No. 4,400,619. The stimulable phosphor sheet 102 erased at the erasing section 130 is sent again to the image recording section 110. In the course of movement of the stimulable phosphor sheet 102 to the erasing section 130, the stimulable phosphor sheet 102 is cleaned by a cleaning roller 105, and dust is removed from the sheet surface.
However, with the radiation image recording and read-out apparatus as shown in FIG. 5 wherein the overall conveyor 101 is stopped or moved, various problems arise as described below. Specifically, the conveyor 101 must be stopped at the time the image recording is to be carried out at the image recording section 110, and must be moved at the time the image read-out is to be carried out at the image read-out section 120, so that the image recording and the image read-out cannot be carried out at the same time. Therefore, the image recording cannot be carried out as long as the image read-out from the stimulable phosphor sheet 102 is being carried out at the image read-out section 120. A comparatively long time is taken for the image read-out, and therefore the image recording cannot be carried out efficiently in the case where the image recording is to be carried out sequentially for may images. Also, with the radiation image recording and read-out apparatus as shown in FIG. 5, it is not always possible to carry out several image recording steps sequentially and to make wait the image-recorded stimulable phosphor sheets in the region prior to the image read-out section 120. Furthermore, as the conveyor 101 passes over the image read-out section 120 and the erasing section 130 at the same speed, the apparatus cannot satisfy the need that the erasing be carried out substantially by decreasing the speed of conveyance of the stimulable phosphor sheet at the time of the erasing as compared with the image read-out step.